Companies need to take the "embedded water" footprint into account for their products. Photograph: Martin Harvey/ Martin Harvey/CORBIS

The big facts about water are staggering, but it's their very scale that makes them somehow ungraspable. How is anyone meant to get their heads around the miserable fact that in the 21st century two billion people don't have access to basic sanitation and one billion lack access to clean safe water? It's so depressingly big that it's tempting to mentally file it away as too big for any one person to do anything about and let it sit there sulking along with doubts about climate change and angst on recycling.

And even from a corporate point of view the picture at first glance looks tough to do anything about. For example, take the company I work for, Unilever. We've spent a lot of effort and scientific rigour measuring how much water we use to make the products we sell and found that just about all of it was outside our direct control. Half of it is tied up in the irrigation water used to grow the crops we use as raw materials and the other half is used by our consumers when they wash their clothes or themselves in the shower. At first glance it looks like another ungraspable problem.

But the reality is very different. One of the smartest concepts that has revolutionised the thinking in this area is "embedded water". Professor Tony Allen's idea of counting all the water used to make an item has enabled the hidden, or embedded water in everyday objects to be made visible, which in turn makes it possible to start thinking about the actions needed to reduce the amount. The humble and everyday cup of latte in your hand becomes a 200 litre water bill (143 litres to grow the coffee, 50 for the milk and a mere 2.5 litres for the plastic lid) and your 8oz steak takes 3,400 litres to reach your plate.

The water footprint community, led out of the University of Twente in the Netherlands has been able to extend the original idea into measuring the water demands of their entire country, which in turn has enabled the Dutch government to have an idea of their embedded water imports. Countries can now see where their water vulnerabilities lie and make decisions about the types of crops they want to grow compared to the water they have available. A great example is in the Murray-Darling basin in Australia, where water shortages have forced the change away from low revenue earning crops like wheat, to high earners like grapes (and hence wine) to make the best commercial use of the small amount of available water.

But what about individuals, what can you and I do and why should we care? Does it matter that the tasty asparagus we buy is being grown in the desert in Peru, or that our average personal daily consumption of water is 160 litres of water a day in the UK? When you compare it to the US (575 litres per person, per day) it seems quite low, but, despite the traditional perception that it always rains in the UK, my Liverpool home had a hosepipe ban all summer this year and London's first desalination plant came on line in June this year in order to help meet the capital's thirst for water. Critics of the London scheme would rather we all had water meters and spent more effort on fixing the 217 litres of leakage a day from each property that is the legacy of an ageing water infrastructure.

But the fact is that taking small actions can have a big difference. Making sure you always fill the drum of your washing machine instead of washing a few socks saves water as does taking slightly shorter showers. Companies are starting to make decisions about the raw materials they buy, based on sustainability criteria such as Rainforest Alliance certification and the next extension of this will be a form of water stewardship.

The water dilemma of Peruvian asparagus versus economic development will be played out over a thousand raw materials and gradually the water impact of agriculture will be reduced through working with farmers. It won't solve the sanitation problem in Asia, that's going to take the concerted efforts of NGOs and governments over decades, but taking individual responsibility starts the journey of a thousand steps.

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